rsync is a program that behaves in much the same way that
rcp does, but has many more options and uses the rsync
remote-update protocol to greatly speedup file transfers
when the destination file already exists.
The rsync home page has
more information.

The rsync remote-update protocol lets rsync transfer
just the differences between two sets of files across the
network link, using an efficient checksum-search algorithm
described in the technical report that accompanies this
package.

Some of the additional features of rsync are:

support for copying links, devices, owners, groups and permissions

exclude and exclude-from options similar to GNU tar

a CVS exclude mode for ignoring the same files that CVS would ignore

can use any transparent remote shell, including rsh or ssh

does not require root privileges

pipelining of file transfers to minimize latency costs

support for anonymous or authenticated rsync servers (ideal for mirroring)

Note: this is not the same program as /usr/sbin/rsync.
An error message like:

usually means that the wrong rsync was found on the remote machine,
either because the freeware rsync wasn't installed, or because
of PATH problems (see the --rsync-path option). This
build uses --rsync-path=/usr/freeware/bin/rsync by default.

To auto-install this package, go back and click on the respective install icon.